Intravascular arterial to venous anastomosis and tissue welding catheter and methods

ABSTRACT

Systems and methods for creating an arteriovenous (AV) fistula comprise an elongate member, a distal member connected to the elongate member and movable relative to the elongate member, and a heating member disposed on at least one of the movable distal member and the elongate member. The distal member comprises structure for capturing tissue to be cut to create the fistula, and the heating member is adapted to cut through the tissue to create the fistula. The elongate member comprises an elongate outer tube. A shaft connects the distal member to the elongate member, and is extendable and retractable to extend and retract the distal member relative to the elongate member.

This application is a continuation under 35 U.S.C. 120 of U.S. patentapplication Ser. No. 15/136,794, entitled Intravascular Arterial toVenous Anastomosis and Tissue Welding Catheter, filed on Apr. 22, 2016,which will issue as U.S. Pat. No. 9,931,164 on Apr. 3, 2018, which inturn is a divisional under 35 U.S.C. 120 of U.S. patent application Ser.No. 13/161,356, entitled Intravascular Arterial to Venous Anastomosisand Tissue Welding Catheter, filed on Jun. 15, 2011, now issued as U.S.Pat. No. 9,452,015, which in turn claims the benefit under 35 U.S.C.119(e) of the filing date of Provisional U.S. Application Ser. No.61/354,903, entitled Systems and Methods for Creating ArteriovenousFistulas, filed on Jun. 15, 2010, and Provisional U.S. Application Ser.No. 61/480,818, entitled Intravascular Arterial to Venous Anastomosisand Tissue Welding Catheter, filed on Apr. 29, 2011. All of theforegoing commonly assigned applications are expressly incorporatedherein by reference, in their entirety.

BACKGROUND OF THE INVENTION

In the body, various fluids are transported through conduits throughoutthe organism to perform various essential functions. Blood vessels,arteries, veins, and capillaries carry blood throughout the body,carrying nutrients and waste products to different organs and tissuesfor processing. Bile ducts carry bile from the liver to the duodenum.Ureters carry urine from the kidneys to the bladder. The intestinescarry nutrients and waste products from the mouth to the anus.

In medical practice, there is often a need to connect conduits to oneanother or to a replacement conduit to treat disease or dysfunction ofthe existing conduits. The connection created between conduits is calledan anastomosis.

In blood vessels, anastomoses are made between veins and arteries,arteries and arteries, or veins and veins. The purpose of theseconnections is to create either a high flow connection, or fistula,between an artery and a vein, or to carry blood around an obstruction ina replacement conduit, or bypass. The conduit for a bypass is a vein,artery, or prosthetic graft.

An anastomosis is created during surgery by bringing two vessels or aconduit into direct contact. The vessels are joined together with sutureor clips. The anastomosis can be end-to-end, end-to-side, orside-to-side. In blood vessels, the anastomosis is elliptical in shapeand is most commonly sewn by hand with a continuous suture. Othermethods for anastomosis creation have been used including carbon dioxidelaser, and a number of methods using various connecting prosthesis,clips, and stents.

An arterio-venous fistula (AVF) is created by connecting an artery to avein. This type of connection is used for hemodialysis, to increaseexercise tolerance, to keep an artery or vein open, or to providereliable access for chemotherapy.

An alternative is to connect a prosthetic graft from an artery to a veinfor the same purpose of creating a high flow connection between arteryand vein. This is called an arterio-venous graft, and requires twoanastomoses. One is between artery and graft, and the second is betweengraft and vein.

A bypass is similar to an arteriovenous graft. To bypass an obstruction,two anastomoses and a conduit are required. A proximal anastomosis iscreated from a blood vessel to a conduit. The conduit extends around theobstruction, and a second distal anastomosis is created between theconduit and vessel beyond the obstruction.

As noted above, in current medical practice, it is desirable to connectarteries to veins to create a fistula for the purpose of hemodialysis.The process of hemodialysis requires the removal of blood from the bodyat a rapid rate, passing the blood through a dialysis machine, andreturning the blood to the body. The access to the blood circulation isachieved with catheters placed in large veins, prosthetic graftsattached to an artery and a vein, or a fistula where an artery isattached directly to the vein.

Fistulas for hemodialysis are required by patients with kidney failure.The fistula provides a high flow of blood that can be withdrawn from thebody into a dialysis machine to remove waste products and then returnedto the body. The blood is withdrawn through a large access needle nearthe artery and returned to the fistula through a second large returnneedle. These fistulas are typically created in the forearm, upper arm,less frequently in the thigh, and in rare cases, elsewhere in the body.It is important that the fistula be able to achieve a flow rate of 500ml per minute or greater. Dialysis fistulas have to be close to the skin(<6 mm), and large enough (>4 mm) to access with a large needle. Thefistula needs to be long enough (>6 cm) to allow adequate separation ofthe access and return needle to prevent recirculation of dialyzed andnon-dialyzed blood between the needles inserted in the fistula.

Fistulas are created in anesthetized patients by carefully dissecting anartery and vein from their surrounding tissue, and sewing the vesselstogether with fine suture or clips. The connection thus created is ananastomosis. It is highly desirable to be able to make the anastomosisquickly, reliably, with less dissection, and with less pain. It isimportant that the anastomosis is the correct size, is smooth, and thatthe artery and vein are not twisted.

SUMMARY OF THE INVENTION

The present disclosed invention eliminates the above described openprocedures, reduces operating time, and allows for a consistent andrepeatable fistula creation.

It is well known that heat, whether its source is Radio Frequency (RF),resistance, or laser, will attach and weld tissue or vessels upon directpressure and contact over the targeted weld area. This is often donewith jaw-type, compression heat delivery devices. It is also well knownthat radially expandable devices such as balloons, metal cages, andbaskets are often coupled with energy in the form of RF, or in the caseof balloons, heated saline, and used intraluminally to ablate tissue,stop bleeding, or create a stricture.

The present invention uses catheter based devices that are advanced fromone vessel into an adjacent vessel (i.e. a vein into an artery), jointhe vessel walls by applying heat, and cut through the two walls,creating an anastomosis.

The inventive catheter-based devices track over a guidewire which hasbeen placed from a first vessel, such as a vein, into a second vessel,such as an artery, or more broadly between any other two vascularstructures. The distal tip of the catheter has a dilating tip whichallows the catheter to advance easily through the vessel walls. Proximalto the distal tip, the catheter has a significant reduction in diameter,and then a blunt, oval shaped tapered surface. As the catheter istracked over the guidewire, the tapered distal tip easily passes intothe adjacent vessel. As the catheter is further advanced, the bluntproximal surface comes into contact with the wall of the first vesseland encounters resistance, and cannot perforate through the wall intothe second vessel. The distal tip, which has a matching blunt surface onits proximal end, is then retracted, capturing the walls of the twovessels between the two blunt surfaces. A known, controlled pressure(approximately 100 mN/mm²-300 mN/mm²) is applied between the twosurfaces. The pressure can be controlled either internally in thecatheter or by the handle attached to the proximal end of the catheter.Heat is then applied to the blunt surfaces to weld the walls of the twovessels together. It is possible to only apply the heat to one surfaceas well. Heat can be applied through several different methods,including, but not limited to, radiofrequency, resistance, inductance,or a combination thereof. The heat is controlled at a known temperatureranging from between about 100-150 C. The heat may be applied by eitherapplying a steady heat, pulsing heat, or a combination thereof.

After coaptation of the vessel walls, the heat is then increased to cutthrough the vessel walls to create the desired size fistula. It shouldbe noted that it is also possible to apply the same heat to both weldthe vessel walls and to cut through the vessel.

More particularly, there is provided a device for creating anarteriovenous (AV) fistula, which comprises an elongate member, a distalmember connected to the elongate member and movable relative to theelongate member, and a heating member disposed on at least one of themovable distal member and the elongate member. The distal membercomprises structure for capturing tissue to be cut to create thefistula, and the heating member is adapted to cut through the tissue tocreate the fistula. The elongate member comprises an elongate outertube.

A shaft connects the distal member to the elongate member, and isextendable and retractable to extend and retract the distal memberrelative to the elongate member. Preferably, the elongate membercomprises a distal tapered face and the distal member comprises aproximal tapered face, wherein the distal tapered face and the proximaltapered face are substantially aligned to one another. In someembodiments, the heating member is disposed on the proximal taperedface, while in other embodiments, the heating member is disposed on thedistal tapered face. Some embodiments further comprise a second heatingmember disposed on the distal tapered face. At least one of the heatingmember and the second heating member comprises an energized heater and aheat spreader disposed beneath the energized heater to spread heat awayfrom the heater and create a temperature gradient. The heat spreadercomprises heat conductive material, and is disposed on the tapered facebeneath the heating member.

Preferably, the distal member is tapered and flexible, so that it canpush through a small aperture between the two vessels to be joined witha fistula. In some embodiments, the distal member comprises a togglemember which is pivotal relative to the elongate member. In certainembodiments, a shaft is provided for connecting the toggle member to theelongate member, the shaft being extendable and retractable to extendand retract the toggle member relative to the elongate member, whereinthe toggle member is pivotally connected to the shaft.

In one disclosed embodiment, the distal member comprises a flexibleclamp to which is connected a heater, wherein the clamp is movablerelative to the elongate member and is adapted to capture tissue to becut to create the fistula. In this embodiment, the distal member furthercomprises a distal portion connected to a distal end of the elongatemember, the distal portion having a side port therein through which theflexible clamp and connected heater extend.

A tissue receiving cavity may be associated with the heating member, tocapture cut tissue. As noted above, in some embodiments, the heatingmember comprises an energized heater and a heat spreader disposedbeneath the energized heater to spread heat away from the heater andcreate a temperature gradient. The heat spreader comprises heatconductive material.

In another aspect of the invention, there is disclosed a method ofcreating an AV fistula between adjacent first and second vessels, whichcomprises a step of inserting a guidewire from the first vessel into thesecond vessel, inserting a catheter comprising a proximal elongatemember and a distal member over the guidewire, so that a tapered distaltip of the distal member comes into contact with a selected anastomosissite, and advancing the distal member into the second vessel, while theelongate member remains in the first vessel, thereby enlarging anaperture between the two vessels. A further step involves retracting thedistal member toward the elongate member to clamp tissue surrounding theaperture between opposed surfaces on each of the distal member and theelongate member, and applying energy to a heating member on one of thedistal member and the elongate member to cut and form the aperture, andto weld the edges thereof in order to create a desired fistula betweenthe two vessels.

Preferably, the opposed surfaces on each of the distal member and theelongate member comprise aligned blunt facing tapered faces, betweenwhich the tissue is clamped, wherein a heating member is disposed on atleast one of the two aligned tapered faces. The method mayadvantageously further comprise a step of capturing cut tissue within acavity disposed adjacent to the heating member. Heat may be dispersedaway from the heating member using a heat spreader comprising aconductive material disposed on the tapered surface beneath the heatingmember.

The advancing step may comprise moving the distal member distallyrelative to the elongate member so that the distal member is spaced agreater axial distance from the elongate member after the advancing stepis performed than it was before the advancing step is performed. Theretracting step may comprise moving the distal member proximallyrelative to the elongate member so that the distal member is spaced alesser axial distance from the elongate member after the retracting stepis performed than it was before the retracting step is performed. Insome applications, the catheter is rotated during the advancing step.

The advancing step is performed by advancing a central tubular structuredistally from an outer tube comprising the elongate member, and theretracting step is performed by withdrawing the central tubularstructure proximally into the outer tube. The retracting step includes astep of applying a slight tension to a heating element on the distalmember to seat the heating element against a wall of the second vessel.The method further comprises a step of advancing the outer tube afterthe retracting step, until a distal end of the outer tube contacts awall of the first vessel, thereby clamping tissue surrounding theaperture between opposed surfaces on each of the distal member and theelongate member. The energy applying step comprises a tissue cuttingstep followed by a tissue welding step, the tissue welding step beingmanaged to cauterize and weld edges of the aperture formed during thetissue cutting step.

The method may include a further step of creating the aperture by usinga needle to puncture a wall of the first vessel and an adjacent wall ofthe second vessel, prior to the step of inserting a guidewire.

In another aspect of the invention, there is disclosed a method ofcreating an AV fistula between adjacent first and second vessels. Themethod includes steps of inserting a guidewire from the first vesselinto the second vessel, and inserting a catheter comprising a proximalelongate member and a distal member over the guidewire, so that atapered distal tip of the distal member comes into contact with aselected anastomosis site. Further steps include advancing the distalmember into the second vessel, until a distal face of the elongatemember contacts a tissue wall of the first vessel, so that the elongatemember remains in the first vessel, thereby enlarging an aperturebetween the two vessels, and retracting the distal member toward theelongate member, until a proximal face of the distal member contacts atissue wall of the second vessel. An additional step comprises applyingenergy to a heating member on one of the distal member and the elongatemember to cut and form the aperture, and to weld the edges thereof inorder to create a desired fistula between the two vessels.

For the foregoing method, the distal face of the elongate member and theproximal face of the distal member comprise aligned blunt facing taperedsurfaces, between which the tissue is clamped, wherein the heatingmember is disposed on one of the distal and proximal aligned bluntfacing tapered surfaces. An additional method step comprises dispersingheat away from the heating member using a heat spreader comprising aconductive material disposed on the blunt tapered surface beneath theheating member. The advancing step comprises moving the distal memberdistally relative to the elongate member so that the distal member isspaced a greater axial distance from the elongate member after theadvancing step is performed than it was before the advancing step isperformed.

The retracting step comprises moving the distal member proximallyrelative to the elongate member so that the distal member is spaced alesser axial distance from the elongate member after the retracting stepis performed than it was before the retracting step is performed.

The advancing step is performed by advancing a central tubular structuredistally from an outer tube comprising the elongate member, and theretracting step is performed by withdrawing the central tubularstructure proximally into the outer tube. The energy applying stepcomprises a tissue cutting step followed by a tissue welding step, thetissue welding step being managed to cauterize and weld edges of theaperture formed during the tissue cutting step.

The invention, together with additional features and advantages thereof,may best be understood by reference to the following description takenin conjunction with the accompanying illustrative drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of an embodiment of a catheter deviceconstructed in accordance with the principles of the present invention;

FIGS. 2-8 are schematic sequential views illustrating a method forcreating a fistula performed in accordance with the principles of thepresent invention, and using an apparatus like that illustrated in FIG.1 and disclosed herein;

FIG. 9 is a schematic view illustrating an elongate aperture formedbetween two adjacent vessels to create the fistula, particularlyhighlighting the welded edges of the aperture;

FIG. 10 is a cross-sectional view of a handle portion of the embodimentshown in FIG. 1;

FIG. 11 is an isometric view similar to FIG. 1, illustrating analternative embodiment of the invention;

FIG. 12 is an isometric view of yet another alternative embodiment ofthe present invention;

FIG. 13 is an isometric view of still another alternative embodiment ofthe present invention, wherein a distal toggle member forming part ofthe device is extended;

FIG. 14 is an isometric view similar to FIG. 13, wherein the distaltoggle member is retracted;

FIG. 15 is an isometric view of yet another alternative embodiment ofthe present invention; and

FIGS. 16-18 are schematic sequential views illustrating a method forcreating a fistula using the apparatus of FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now particularly to the drawings, there is shown in FIG. 1 abi-polar tapered tip catheter embodiment 10, which comprises an elongateouter tube 12 having an outer diameter that can range from 3 F-12 F. Itmay be manufactured from a variety of materials, either polymer ormetallic. It comprises a central lumen 14, within which a tubularstructure 16 for attaching a tip 18 may slide. There are separate luminathat run down the elongated core of the outer tube 12 for wiring topower electrodes or heating elements 20, 22 (proximal and distal,respectively), disposed on aligned tapered faces of the respectiveelongate outer tube 12 and distal tip 18, and to also measure thetemperature during the coaptation and cutting processes. In thisconfiguration, the catheter is powered using bipolar energy to thedistal RF electrode 22 and the proximal RF electrode 20. The system canalso be used in a monopolar configuration by grounding the patient andapplying energy to one or both of the RF electrodes to increase thelength of the coaptation. The RF electrodes cut at matching angles toincrease the surface area of the coaptation and fistula size relative tothe catheter diameter. These angles can be adjusted to achieve thedesired fistula sizing. The RF electrodes are only electricallyconductive on the front faces to maximize energy density. The electrodesare oval-shaped, and are adapted to cut an anastomosis which is largerthan the diameter of the shaft 16.

The apparatus shown and described above in connection with FIG. 1 willnow be further described in conjunction with an explanation of aparticular method by which the system 10 may be used to create an AVfistula. This method is illustrated more particularly in FIGS. 2-9.

To begin the inventive method of creating an AV fistula, thepractitioner selects an appropriate procedural site having each of afirst vessel 26 and a second vessel 28 in close proximity to oneanother. In currently preferred approaches, the first vessel 26comprises a vein, and the second vessel 28 comprises an artery, but theinvention is not necessarily limited to this arrangement. As illustratedin FIG. 2, one presently preferred location is the hand 30 of a patient.Then, generally employing principles of the Seldinger technique, asshown in FIG. 2, the first vessel 26 is punctured by a needle 32, whichis inserted therein, for the purpose of introducing an access sheathinto the site. Then, using suitable techniques, such as the techniquedescribed in Provisional U.S. Application Ser. No. 61/354,903, filed onJun. 15, 2010 and herein expressly incorporated by reference, in itsentirety, a guidewire 34 is inserted into the patient, from the firstvessel 26 into the second vessel 28, as shown in FIG. 3.

The guidewire 34 creates an access path for the catheter 10. Thecatheter 10 is inserted into the patient by loading a proximal end ofthe guidewire 34 into the tip 18, which is fabricated to be flexible andtapered. The catheter 10 is advanced further into the patient, trackingover the guidewire 34, until the tapered dilating distal tip 18 comesinto contact with the selected anastomosis site. The device 10 can betracked over the guidewire with the distal tip extended (as shown inFIG. 5) or retracted (as shown in FIG. 4). The distal tip 18 is extendedand further advanced into the second vessel 28 (FIG. 5) by advancing thecentral tubular structure 16 distally from the outer tube 12, therebydilating the fistula, so that the distal tip 18 is in the second vessel28, and the tube 12 is in the first vessel 26, with its distal taperedsurface contacting the inner wall of the first vessel 26. If resistanceis felt, the entire system can be rotated to reduce the friction. Atthis juncture, the opening formed in the wall of the second vessel 28has recovered back to a small diameter, and fits tightly around theshaft 16, as shown.

After the distal tip 18 is advanced into the second vessel 28, asillustrated in FIG. 6, a slight tension is applied to the distal RFelectrode 22 to seat it against the vessel wall. The blunt shape of theproximal end of the distal tip 18 prevents the distal tip from pullingback through the vessel wall. The proximal end of the device 10, namelythe outer tube 12, is then advanced to close the spacing between thetube 12 and tip 18, until the walls of the first and second vessels 26,28, respectively, are captured between the facing blunt surfaces of eachof the outer tube 12 and distal tip 18.

A controlled tension is maintained between the distal tip 18 andproximal outer tube 12, and at this juncture, with the vessel wallssecurely clamped, energy is applied to the RF electrodes 20, 22 (FIG.7). As the electrodes weld and cut the vessels, the electrodes will movecloser to one another. When fully retracted, the system 10 is designedso that the two electrodes 20, 22 cannot come into direct contact withone another, thus preventing the electrodes from shorting. A variety ofRF energy profiles may be applied to achieve the desired coaptation andcutting. For example, during the coaptation phase, a tapered sine wavemay be applied to maximize coagulation without cutting through thetissue. The energy may also be adjusted based upon the impedance of thetissue. Different pulse widths or duty cycles may be used to minimizethe heat transferring into adjacent tissues. The hot wire is an ovalshape and cuts an anastomosis larger than the diameter of the shaft 16.Within the oval shape of the cutting elements, there is a cavity forcapturing the tissue that has been cut. The outer sliding tube is usableto push the tissue off the heater in case there is a sticking problemdue to the heat.

Regarding the tissue welding process, more particularly, the RF energyfunctions to burn and fuse or weld the vessels together, creating anelongate aperture 36 (FIG. 8) through the opposing walls of each of thefirst and second vessels, as well as any intervening tissue. As formed,the elongate aperture 36 will typically resemble a slit. However, aspressurized flow 38 begins to occur through the slit or aperture 36,which creates a communicating passage between the first vessel and thesecond vessel, the aperture widens responsive to the pressure, takingthe shape of an ellipse as it opens to form the desired fistula. Thiseffect is illustrated in FIG. 9. The edges 40 of the aperture arecauterized and welded. FIG. 9 illustrates the weld from the venous(first vessel) side. As shown, the cut area corresponds to the shape ofthe heater wire. It can be of multiple shapes, such as round, oval, aslit, or a combination as shown. The area outside of the cut has beenwelded due to the flat face of the catheter in the vein (first vessel)being larger than the cutting wire. The heat from the wire is alsopreferably spread over this area by a conductive material that is belowthe heater, as will be described below. This creates a temperaturegradient, which is a particularly advantageous feature of the presentinvention.

Tissue welding of the type intended to occur in the practice of theseinventive methods is discussed in U.S. Pat. No. 6,908,463, to Treat etal., which is herein expressly incorporated by reference, in itsentirety.

FIG. 10 is a cross-sectional view of a handle portion 42 of theembodiment shown in FIG. 1. This is one possible approach for actuatingthe extension and retraction of the distal tip 18 relative to theelongate outer tube 12, as discussed above, though many other suitableconfigurations may be used alternatively. A trigger 44 is slideablydisposed on the handle 42, slidable distally through a slot 46 in thedirection of arrow 48, and then retractable in the reverse direction. Aspring 50 within the handle controls pressure, and a locking mechanismfunctions to lock the trigger 44 in the retracted state.

Alternative cutting approaches, such as resistive heat (hot wire),ultrasonic, laser, or mechanical approaches, may be used instead of RFenergy, if desired. For example, FIG. 11 illustrates an alternativeembodiment, wherein a catheter 110 comprises an elongate outer tube 112having a central lumen 114, a tubular structure 116, and a flexible andtapered distal tip 118. In this embodiment, a single resistive heatingwire 152 is used to provide the tissue heating, cutting, and weldingfunction described above. Additionally, an RF configuration applyingonly monopolar energy, to either the venous or arterial sides, may beemployed. A combination of RF energy and resistance heating may also beused. The tip 118, in this embodiment, tracks over the guidewire anddilates the anastomosis site, as in the previous embodiment. The taperedfaces of the members 112 and 118 align. The single hot wire 152 down theface cuts a slit in the vessel walls, and the faces are tapered toassist in removing the device.

Now with reference to FIG. 12, a heat spread catheter 210 isillustrated. The catheter 210 comprises a resistive heating element 252,which is employed in a manner similar to that described above inconnection with the FIG. 11 embodiment. However, in this embodiment, aconductive material 254 is disposed beneath the heating element 252. Inone configuration, this conductive material 254 comprises aluminum,though other conductive bio-compatible materials may also be used. Inoperation, this conductive material 254 functions to create a heatgradient from the heating element 252, for the purpose of improving thewelding function, as described above.

In this embodiment, similar to the foregoing embodiments, the tip 218tracks over the guidewire and dilates the anastomosis site. The taperedfaces of each of the members 212 and 218 align, for clamping the vesselwalls. The hot wire 252 is an oval shape and has vertical strips 256 onboth sides of the artery. The hot wire cuts an anastomosis larger thanthe diameter of the shaft 216. Under the hot wire 252, the heatconductive material 254 pulls heat away from the hot wire so that thereis a temperature gradient across the face, with the temperature beinghottest in the center and cooling as the distance outwardly from thecenter increases.

The hot wire 252 (heater) is raised above the spreader 254 to increasepressure on the tissue, to thereby assist in the cutting process. Insidethe hot wire, there is a cavity to capture the tissue that has been cut.The profile of the distal tip 218 aligns with the edge of the heaterwhen retracted. It is a lower profile than the heat spreader, so that itcan be retracted back through the fistula. This also increases thepressure directly on the heater surface to assist in cutting function.

FIGS. 13 and 14 illustrate still another embodiment 310, comprising adistal toggle member 358. The cutting elements in this embodiment aresubstantially identical to those shown and described in connection withFIG. 12. As in prior embodiments, the toggle 358 tracks over theguidewire into the artery. When retracted (FIG. 15), the toggle capturesthe artery and pulls against the vein. The hot wire is an oval shape,has vertical strips 356 on both sides of the artery, and cuts ananastomosis larger than the diameter of the shaft 316. Under the hotwire 352, there is a heat conductive material 356 that pulls heat awayfrom the hot wire so that there is a temperature gradient across theface. The hot wire is raised above the heat spreader to increasepressure on the tissue to help it cut through. Inside the hot wire thereis a cavity to capture the tissue that has been cut.

The profile of the toggle 358 aligns with the edge of the heater whenretracted. It is of a lower profile than the heat spreader so that itcan be retracted back through the fistula. This also increases thepressure directly on the heater surface and helps it cut. Heatingelements may also be disposed on the toggle surface to work inconjunction with the heater 352 to cut and weld tissue.

Pivotable toggles and their functionality are discussed in ProvisionalU.S. Application Ser. No. 61/354,903, filed on Jun. 15, 2010 and alreadyherein expressly incorporated by reference. Those teachings generallyapply to this toggle embodiment, regarding the particulars as to how thetoggle is used to enter and then retract the second vessel toward thefirst vessel.

In FIGS. 15-18, there is shown a different cutting approach. In thisembodiment, the cutting device 410 comprises a shaft 460 having a distalportion 462. The distal portion comprises a side port 464, from whichextends a heater wire 466 which is supported by a flexible clamp 468,preferably fabricated from nitinol or similar material. The heater wiremay be resistive or utilize any other energy source as described above.

As shown in FIGS. 16-18, access to the anastomosis site is gained bymethods as described above and the function of this device, once inplace, is to manipulate the wire 466, using the flexible clamp 468 andsuitable actuation mechanisms in order to create a fistula of a desiredconfiguration. Specifically, as shown in FIG. 16, the tip 462 tracksover the guidewire 34 and dilates the anastomosis site, as in previouslydescribed approaches. The catheter 410 is advanced so that the clip 466is all the way in the artery 28, and then pulled back to capture thearterial wall under the clip, as illustrated in FIG. 17. The wire isthen activated to heat, and then drawn back, which cuts through thearterial and venous walls. The hot wire is then pulled back (FIG. 18),and pulls down the clip portion through the vessel walls.

Accordingly, although an exemplary embodiment and method according tothe invention have been shown and described, it is to be understood thatall the terms used herein are descriptive rather than limiting, and thatmany changes, modifications, and substitutions may be made by one havingordinary skill in the art without departing from the spirit and scope ofthe invention.

1. A device for creating an arteriovenous (AV) fistula, comprising: anelongate member; a distal member connected to the elongate member andmovable relative to the elongate member; and a heating member disposedon at least one of said movable distal member and said elongate member;wherein the distal member comprises structure for capturing tissue to becut to create the fistula, and said heating member is adapted to cutthrough said tissue to create the fistula.
 2. The device as recited inclaim 1, wherein said elongate member comprises an elongate outer tube.3. The device as recited in claim 1, and further comprising a shaft forconnecting the distal member to the elongate member, the shaft beingextendable and retractable to extend and retract said distal memberrelative to the elongate member.
 4. The device as recited in claim 1,wherein said elongate member comprises a distal tapered face and saiddistal member comprises a proximal tapered face, and further whereinsaid distal tapered face and said proximal tapered face aresubstantially aligned to one another.
 5. The device as recited in claim4, wherein said heating member is disposed on said proximal taperedface.
 6. The device as recited in claim 5, and further comprising asecond heating member disposed on said distal tapered face.
 7. Thedevice as recited in claim 6, wherein at least one of said heatingmember and said second heating member comprises an energized heater anda heat spreader disposed beneath the energized heater to spread heataway from the heater and create a temperature gradient.
 8. (canceled) 9.The device as recited in claim 1, wherein said distal member is taperedand flexible.
 10. The device as recited in claim 1, wherein said distalmember comprises a toggle member which is pivotal relative to saidelongate member.
 11. The device as recited in claim 10, and furthercomprising a shaft for connecting the toggle member to the elongatemember, the shaft being extendable and retractable to extend and retractthe toggle member relative to the elongate member, said toggle memberbeing pivotally connected to said shaft.
 12. The device as recited inclaim 1, wherein said distal member comprises a flexible clamp to whichis connected a heater, said clamp being movable relative to saidelongate member and being adapted to capture tissue to be cut to createthe fistula.
 13. The device as recited in claim 12, wherein said distalmember further comprises a distal portion connected to a distal end ofthe elongate member, the distal portion having a side port thereinthrough which said flexible clamp and connected heater extend.
 14. Thedevice as recited in claim 4, wherein said heating member is disposed onsaid distal tapered face of said elongate member.
 15. The device asrecited in claim 14, and further comprising a tissue receiving cavityassociated with said heating member.
 16. The device as recited in claim14, wherein said heating member comprises an energized heater and a heatspreader disposed beneath the energized heater to spread heat away fromthe heater and create a temperature gradient.
 17. (canceled)
 18. Amethod of creating an AV fistula between adjacent first and secondvessels, comprising: inserting a guidewire from the first vessel intothe second vessel; inserting a catheter comprising a proximal elongatemember and a distal member over the guidewire, so that a tapered distaltip of the distal member comes into contact with a selected anastomosissite; advancing the distal member into the second vessel, while theelongate member remains in the first vessel, thereby enlarging anaperture between the two vessels; retracting the distal member towardthe elongate member to clamp tissue surrounding the aperture betweenopposed surfaces on each of the distal member and the elongate member;and applying energy to a heating member on one of the distal member andthe elongate member to cut and form the aperture, and to weld the edgesthereof in order to create a desired fistula between the two vessels.19. The method as recited in claim 18, wherein the opposed surfaces oneach of the distal member and the elongate member comprise alignedtapered faces, between which the tissue is clamped, wherein a heatingmember is disposed on at least one of the two aligned tapered faces. 20.The method as recited in claim 19, and further comprising a step ofcapturing cut tissue within a cavity disposed adjacent to the heatingmember.
 21. The method as recited in claim 19, and further comprisingdispersing heat away from the heating member using a heat spreadercomprising a conductive material disposed on the tapered face beneaththe heating member.
 22. The method as recited in claim 18, wherein theadvancing step comprises moving the distal member distally relative tothe elongate member so that the distal member is spaced a greater axialdistance from the elongate member after the advancing step is performedthan it was before the advancing step is performed.
 23. The method asrecited in claim 22, wherein the retracting step comprises moving thedistal member proximally relative to the elongate member so that thedistal member is spaced a lesser axial distance from the elongate memberafter the retracting step is performed than it was before the retractingstep is performed.
 24. (canceled)
 25. The method as recited in claim 23,wherein the advancing step is performed by advancing a central tubularstructure distally from an outer tube comprising the elongate member,and the retracting step is performed by withdrawing the central tubularstructure proximally into the outer tube.
 26. (canceled)
 27. The methodas recited in claim 23, and further comprising a step of advancing theouter tube after the retracting step, until a distal end of the outertube contacts a wall of the first vessel, thereby clamping tissuesurrounding the aperture between opposed surfaces on each of the distalmember and the elongate member.
 28. The method as recited in claim 18,wherein the energy applying step comprises a tissue cutting stepfollowed by a tissue welding step, the tissue welding step being managedto cauterize and weld edges of the aperture formed during the tissuecutting step.
 29. The method as recited in claim 18, and furthercomprising a step of creating said aperture by using a needle topuncture a wall of the first vessel and an adjacent wall of the secondvessel, prior to the step of inserting a guidewire.
 30. A method ofcreating an AV fistula between adjacent first and second vessels,comprising: inserting a guidewire from the first vessel into the secondvessel; inserting a catheter comprising a proximal elongate member and adistal member over the guidewire, so that a tapered distal tip of thedistal member comes into contact with a selected anastomosis site;advancing the distal member into the second vessel, until a distal faceof the elongate member contacts a tissue wall of the first vessel, sothat the elongate member remains in the first vessel, thereby enlargingan aperture between the two vessels; retracting the distal member towardthe elongate member, until a proximal face of the distal member contactsa tissue wall of the second vessel; and applying energy to a heatingmember on one of the distal member and the elongate member to cut andform the aperture, and to weld the edges thereof in order to create adesired fistula between the two vessels.
 31. The method as recited inclaim 30, wherein the distal face of the elongate member and theproximal face of the distal member comprise aligned blunt facing taperedsurfaces, between which the tissue is clamped, wherein the heatingmember is disposed on one of the distal and proximal aligned bluntfacing tapered surfaces.
 32. The method as recited in claim 31, andfurther comprising dispersing heat away from the heating member using aheat spreader comprising a conductive material disposed on the blunttapered surface beneath the heating member.
 33. The method as recited inclaim 30, wherein the advancing step comprises moving the distal memberdistally relative to the elongate member so that the distal member isspaced a greater axial distance from the elongate member after theadvancing step is performed than it was before the advancing step isperformed.
 34. The method as recited in claim 33, wherein the retractingstep comprises moving the distal member proximally relative to theelongate member so that the distal member is spaced a lesser axialdistance from the elongate member after the retracting step is performedthan it was before the retracting step is performed.
 35. The method asrecited in claim 34, wherein the advancing step is performed byadvancing a central tubular structure distally from an outer tubecomprising the elongate member, and the retracting step is performed bywithdrawing the central tubular structure proximally into the outertube.